MBMS bearer handling

ABSTRACT

There is provided mechanisms for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system. A method is performed by a control node. The method comprises obtaining a need for a new MBMS bearer to be activated. The method comprises activating the new MBMS bearer. The method comprises announcing MBMS bearer identity and complementary service announcement information of the new MBMS bearer on an already announced MBMS bearer, thereby announcing the new MBMS bearer.

TECHNICAL FIELD

Embodiments presented herein relate to multimedia broadcast multicastservice (MBMS) bearer handling, and particularly to methods, a controlnode, a client node, computer programs, and a computer program productfor MBMS bearer handling in a group communications system.

BACKGROUND

In communications networks, there may be a challenge to obtain goodperformance and capacity for a given communications protocol, itsparameters and the physical environment in which the communicationsnetwork is deployed.

An example of applications available in some communications system isgroup communications services. In general terms, group communicationmeans that the same information or media is delivered to multiple clientnodes. In group communication systems (e.g., Push-To-Talk (PTT) systems)the client nodes receiving the same media constitute a group of clientnodes. These client nodes may be located at different locations. If manyclient nodes are located within the same area, multicast or broadcastbased transmission using e.g., Multicast-Broadcast Multimedia Services(MBMS) is efficient for communications to the group of client nodes,because communications resources such as time and frequency resourcesare shared among client nodes. If client nodes are spread out over alarge geographical area it can be more efficient to use unicasttransmission for communications to the group of client nodes.

Before using MBMS there are two different activities that currently mustbe performed.

Firstly, an MBMS bearer must be activated. This will enable media to besent over the network and be broadcasted to wireless devices hosting theclient nodes. In a 3rd Generation Partnership Project (3GPP) Long Termevolution (LTE) network this is initiated in a Broadcast MulticastService Center (BMSC) as defined in 3GPP TS 23.246 v13.2.0.

Secondly, the client nodes must be informed of the service beingbroadcasted over the MBMS bearer. This is required so that the clientnodes know how to receive the media over the MBMS bearer. This procedureis commonly known as a service announcement procedure and is defined in3GPP TS 26.346 v13.2.0.

The information sent in the service announcement message includesseveral aspects of the service that shall be broadcasted. For example,it includes a reference to the MBMS bearer, it includes Internetprotocol (IP) address, ports, protocols and codecs used to receive themedia that shall broadcasted. This type of information is currentlyessential in order for the client node to, via its hosting wirelessdevice, receive anything on the MBMS bearer, and is therefore currentlymandatory. Furthermore, the service announcement may contain severalother type of information, such as service area, scheduling information,reception reporting procedures, error correction information, etc.

When using MBMS for group communication both of the above mandatoryactivities must be performed before a group call over MBMS may start.The reason for this is that, at least currently, both bearer activationand service announcement is too time consuming to be performed at thestart of the group call.

The service announcement procedures currently used are eitherinteractive (meaning that the client nodes request the information or acontrol node of the group communications service pushes the informationto the client nodes) or repetitive, for example by on regular intervalbroadcast the information on a known broadcast bearer, which thewireless device may monitor on a regular basis.

Due to the group communications dynamic need for MBMS capacity, and thetime consuming provisioning process (which includes both the activationof the MBMS bearer as well as the service announcement process), it canbe difficult to efficiently use the MBMS capacity for a groupcommunication system such as a PTT system.

Hence, there is a need for mechanisms that enable efficient use of MBMScapacity in a group communications system.

SUMMARY

An object of embodiments herein is to provide efficient use of MBMScapacity in a group communications system.

According to a first aspect there is presented a method for multimediabroadcast multicast service (MBMS) bearer handling in a groupcommunications system. The method is performed by a control node. Themethod comprises obtaining a need for a new MBMS bearer to be activated.The method comprises activating the new MBMS bearer. The methodcomprises announcing MBMS bearer identity and complementary serviceannouncement information of the new MBMS bearer on an already announcedMBMS bearer, thereby announcing the new MBMS bearer.

Advantageously this method provides efficient MBMS bearer handling inthe group communications system.

According to a second aspect there is presented a control node for MBMSbearer handling in a group communications system. The control nodecomprises processing circuitry. The processing circuitry is configuredto cause the control node to obtain a need for a new MBMS bearer to beactivated. The processing circuitry is configured to cause the controlnode to activate the new MBMS bearer. The processing circuitry isconfigured to cause the control node to announce MBMS bearer identityand complementary service announcement information of the new MBMSbearer on an already announced MBMS bearer, thereby announcing the newMBMS bearer.

Advantageously this control node provides efficient MBMS bearer handlingin the group communications system.

According to a third aspect there is presented a control node for MBMSbearer handling in a group communications system. The control nodecomprises processing circuitry and a computer program product. Thecomputer program product stores instructions that, when executed by theprocessing circuitry, causes the control node to perform a set ofoperations, or steps. The operations, or steps, involve obtaining a needfor a new MBMS bearer to be activated. The operations, or steps, involveactivating the new MBMS bearer. The operations, or steps, involveannouncing MBMS bearer identity and complementary service announcementinformation of the new MBMS bearer on an already announced MBMS bearer,thereby announcing the new MBMS bearer.

Advantageously this control node provides efficient MBMS bearer handlingin the group communications system.

According to a fourth aspect there is presented a control node for MBMSbearer handling in a group communications system. The control nodecomprises an obtain module configured to obtain a need for a new MBMSbearer to be activated. The control node comprises an activate moduleconfigured to activate the new MBMS bearer. The control node comprisesan announce module configured to announce MBMS bearer identity andcomplementary service announcement information of the new MBMS bearer onan already announced MBMS bearer, thereby announcing the new MBMSbearer.

Advantageously this control node provides efficient MBMS bearer handlingin the group communications system.

According to a fifth aspect there is presented a computer program forMBMS bearer handling in a group communications system, the computerprogram comprising computer program code which, when run on processingcircuitry of a control node, causes the control node to perform a methodaccording to the first aspect.

Advantageously this computer program provides efficient MBMS bearerhandling in the group communications system.

According to a sixth aspect there is presented a method for multimediabroadcast multicast service (MBMS) bearer handling in a groupcommunications system. The method is performed by a client node. Themethod comprises obtaining a broadcast service announcement of a newMBMS bearer on an already announced MBMS bearer from a control node ofthe group communications system. The service announcement comprises theMBMS bearer identity and complementary service announcement informationof the new MBMS bearer.

Advantageously this method provides efficient MBMS bearer handling inthe group communications system.

According to a seventh aspect there is presented a client node for MBMSbearer handling in a group communications system. The client nodecomprises processing circuitry. The processing circuitry is configuredto cause the client node to obtain a broadcast service announcement of anew MBMS bearer on an already announced MBMS bearer from a control nodeof the group communications system. The service announcement comprisesthe MBMS bearer identity and complementary service announcementinformation of the new MBMS bearer.

Advantageously this client node provides efficient MBMS bearer handlingin the group communications system.

According to an eighth aspect there is presented a client node for MBMSbearer handling in a group communications system. The client nodecomprises processing circuitry and a computer program product. Thecomputer program product storing instructions that, when executed by theprocessing circuitry, causes the client node to obtain a broadcastservice announcement of a new MBMS bearer on an already announced MBMSbearer from a control node of the group communications system. Theservice announcement comprises the MBMS bearer identity andcomplementary service announcement information of the new MBMS bearer.

Advantageously this client node provides efficient MBMS bearer handlingin the group communications system.

According to a ninth aspect there is presented a client node for MBMSbearer handling in a group communications system. The client nodecomprises an obtain module configured to obtain a broadcast serviceannouncement of a new MBMS bearer on an already announced MBMS bearerfrom a control node of the group communications system. The serviceannouncement comprises the MBMS bearer identity and complementaryservice announcement information of the new MBMS bearer.

Advantageously this client node provides efficient MBMS bearer handlingin the group communications system.

According to a tenth aspect there is presented a computer program forMBMS bearer handling in a group communications system, the computerprogram comprising computer program code which, when run on processingcircuitry of a client node, causes the client node to perform a methodaccording to the sixth aspect.

Advantageously this computer program provides efficient MBMS bearerhandling in the group communications system.

According to an eleventh aspect there is presented a computer programproduct comprising a computer program according to at least one of thefifth aspect and the tenth aspect and a computer readable storage mediumon which the computer program is stored. The computer readable storagemedium can be a non-transitory computer readable storage medium.

Advantageously this computer program product provides efficient MBMSbearer handling in the group communications system.

Further advantageously, these methods, these control nodes, these clientnodes, and these computer programs in turn enable efficient use of MBMScapacity in the group communications system.

Further advantageously, these methods, these control nodes, these clientnodes, and these computer programs provide a time efficient serviceannouncement process. This time efficient service announcement processenables the group communication system to utilize the MBMS resourcesdynamically and to on demand adjust services and add new services overMBMS.

Further advantageously, these methods, these control nodes, these clientnodes, and these computer programs allow the client nodes to stay inidle mode and still receive service announcement information in realtime.

It is to be noted that any feature of the first, second, third, fourth,fifth, sixth seventh, eight, ninth, tenth and eleventh aspects may beapplied to any other aspect, wherever appropriate. Likewise, anyadvantage of the first aspect may equally apply to the second, third,fourth, fifth, sixth, seventh, eight, ninth, tenth, and/or eleventhaspect, respectively, and vice versa. Other objectives, features andadvantages of the enclosed embodiments will be apparent from thefollowing detailed disclosure, from the attached dependent claims aswell as from the drawings.

Generally, all terms used in the claims are to be interpreted accordingto their ordinary meaning in the technical field, unless explicitlydefined otherwise herein. All references to “a/an/the element,apparatus, component, means, step, etc.” are to be interpreted openly asreferring to at least one instance of the element, apparatus, component,means, step, etc., unless explicitly stated otherwise. The steps of anymethod disclosed herein do not have to be performed in the exact orderdisclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept is now described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating a communications systemaccording to embodiments;

FIG. 2a is a schematic diagram showing functional units of a controlnode name according to an embodiment;

FIG. 2b is a schematic diagram showing functional modules of a controlnode name according to an embodiment;

FIG. 3a is a schematic diagram showing functional units of a client nodeaccording to an embodiment;

FIG. 3b is a schematic diagram showing functional modules of a clientnode according to an embodiment;

FIG. 4 shows one example of a computer program product comprisingcomputer readable means according to an embodiment;

FIGS. 5, 6, and 7 are flowcharts of methods according to embodiments;

FIG. 8 is a signalling diagram according to prior art; and

FIG. 9 is a signalling diagram according to an embodiment.

DETAILED DESCRIPTION

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which certain embodiments ofthe inventive concept are shown. This inventive concept may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided by way of example so that this disclosure will be thorough andcomplete, and will fully convey the scope of the inventive concept tothose skilled in the art. Like numbers refer to like elements throughoutthe description. Any step or feature illustrated by dashed lines shouldbe regarded as optional.

FIG. 1 is a schematic diagram illustrating a communications system 100where embodiments presented herein can be applied. The communicationssystem 100 is assumed to provide services for group communication andmay hence be regarded as a group communications system. The groupcommunications system 100 is, according to some aspects, a push to talk(PTT) system.

The communications system 100 comprises a radio access network 120, acore network 130, and a service network 140. Particularly, the corenetwork 130 comprises a packet data network gateway (PGW) 131, a servinggateway (SGW) 132, a mobility management entity (MME) 133, a multicellcoordination entity (MCE) 134, a broadcast multicast service centre(BM-SC) 135, and an MBMS gateway (MBMS GW) 136. The PGW 131, SGW 132,MME 133, MCE 134, BM-SC 135, and MBMS GW136 perform functionalities asknown in the art and further description thereof is therefore omitted.

The communications system 100 further comprises at least one controlnode 200 and at least one client node 300 a, 300 b. The at least onecontrol node 200 may be provided in, or installed on, a radio accessnetwork node 110 or in another entity or device in the radio accessnetwork 120, in an entity or device of the core network 130, or in anentity or device of the service network 140. The at least one controlnode 200 could implement the functionality of a group communicationapplication server (GCS AS). Each client node 300 a, 300 b may beprovided in, or installed on, a respective wireless device 150 a, 150 b.The radio access network 120 is operatively connected to the corenetwork 130 which in turn is operatively connected to the servicenetwork 140. The radio access network node 110 thereby enables thewireless devices 150 a, 150 b, and hence the client nodes 300 a, 300 b,to access services and exchange data as provided by the service network140.

Examples of wireless devices 150 a, 150 b include, but are not limitedto, mobile stations, mobile phones, handsets, wireless local loopphones, user equipment (UE), smartphones, laptop computers, and tabletcomputers. Examples of radio access network nodes 110 include, but arenot limited to, radio base stations, base transceiver stations, node Bs,evolved node Bs, and access points. As the skilled person understands,the communications system 100 may comprise a plurality of radio accessnetwork nodes 110, each providing network access to a plurality ofwireless devices 150 a, 150 b. The herein disclosed embodiments are notlimited to any particular number of radio access network nodes 110,client nodes 300 a, 300 b, or wireless devices 150 a, 150 b.

As disclosed above, due to the group communications dynamic need forMBMS capacity, and the time consuming provisioning process, it can bedifficult to efficiently use the MBMS capacity for a group communicationsystem such as a PIT system. Furthermore, to perform an interactiveservice announcement would require that the wireless devices 150 a, 150b hosting the client nodes 150 a, 150 b becomes operatively connected tothe radio access network 110 (by being in radio resource controlconnected (RRC_CONNECTED) mode).

Reference is now made to the signalling diagram of FIG. 8 illustrating amethod according to prior art for activating and announcing two (ormore) MBMS bearers.

S301: One MBMS bearer is activated and announced to the client nodes 300a, 300 b by the control node 200. This MBMS bearer can be used for groupcommunication control messages such as floor control. The client nodes300 a, 300 b in the wireless devices 150 a, 150 b are activelymonitoring this group communication control messages channel.

Steps S302 and S303 are then repeated for each new MBMS bearer thatneeds to be activated and announced. Steps S302 and S303 may occur inany order.

S302: A new MBMS bearer is activated by the control node 200 based on aneed for group communication. This new MBMS bearer can be used tobroadcast the group communication data.

S303: An MBMS service for the new MBMS bearer is (optionally) announcedto the client nodes 300 a, 300 b by the control node 200 according toany of the defined procedures for service announcement in 3GPP TS 26.346v13.2.0. However the service may be inactive (if step S303 is performedbefore S302) as indicated by scheduling information in the serviceannouncement information.

This is an issue in scenarios where there are a large number of wirelessdevices 150 a, 150 b in a small area, since it will lead to that a largenumber of wireless devices 150 a, 150 b are simultaneously switching toradio resource control connected mode when a new service announcementdistributed to a large number of wireless devices 150 a and 150 b. Thismay drain the capacity of one or more radio access network nodes 120 inthe radio access network 110. If service announcement is performed on abroadcast channel the wireless devices 150 a, 150 b are configured toreceive updates repetitive based on a configured time interval. Thisservice announcement also includes all services typically in largeareas. This is not optimal for dynamic and real time serviceannouncement requirements.

According to the embodiments disclosed herein there is proposedmechanisms that enable an optimized service announcement process thatcan be broadcasted over an MBMS bearer carrying a group communicationservice. The service announcement information can be sent in real timeapplication protocol, such as the Real-Time Protocol (RTP), or itscontrolling protocol, the Real-time Transport Control Protocol (RTCP).The optimized service announcement information could be limited to themandatory parts, and may optionally refer to an already announcedservice, which may include more complete information that applies alsoto the new service being announced.

The embodiments disclosed herein thus relate to mechanisms for MBMSbearer handling in a group communications system 100. In order to obtainsuch mechanisms there is provided a control node 200, a method performedby the control node 200, a computer program product comprising code, forexample in the form of a computer program, that when run on processingcircuitry of the control node 200, causes the control node 200 toperform the method. In order to obtain such mechanisms there is furtherprovided a client node 300 a, 300 b, a method performed by the clientnode 300 a, 300 b, and a computer program product comprising code, forexample in the form of a computer program, that when run on processingcircuitry of the client node 300 a, 300 b, causes the client node 300 a,300 b to perform the method.

FIG. 5 is a flow chart illustrating an embodiment of a method for MBMSbearer handling in a group communications system 100 as performed by thecontrol node 200. FIGS. 6 and 7 are flow charts illustrating embodimentsof methods for MBMS bearer handling in a group communications system 100as performed by the client node 300 a, 300 b. The methods areadvantageously provided as computer programs 420 a, 420 b.

Reference is now made to FIG. 5 illustrating a method for MBMS bearerhandling in a group communications system 100 as performed by thecontrol node 200 according to an embodiment.

It is assumed that there is a need for a new MBMS bearer to be activatedin the group communications system 100. The control node 200 istherefore configured to perform step S102:

S102: The control node 200 obtains a need for a new MBMS bearer to beactivated.

The control node 200 then activates the new MBMS bearer. The controlnode 200 is thus configured to perform step S104:

S104: The control node 200 activates the new MBMS bearer.

The MBMS bearer handling in the group communications system 100 is basedon making a service announcement of a new MBMS bearer on an alreadyannounced MBMS bearer, where the service announcement comprisescomplementary service announcement information. Hence, the control node200 announces the new MBMS bearer according to step S106:

S106: The control node 200 announces MBMS bearer identity andcomplementary service announcement information of the new MBMS bearer onan already announced MBMS bearer. The new MBMS bearer is therebyannounced.

This enables the control node 200 to quickly announce new services overa known MBMS bearer. It allows the client nodes 300 a, 300 b to stay inidle mode and still receive information of the new MBMS service. Thisallows rapid modification of MBMS capacity allocation to dynamicallymeet the current needs of the group communications system 100. It alsoavoids massive unicast transmissions of service announcements.

Embodiments relating to further details of MBMS bearer handling in thegroup communications system 100 relating to the control node 200 willnow be disclosed.

There may be different purposes for activating the new MBMS bearer.According to some aspects the new MBMS bearer is activated forsupporting media transmission in a group call of the groupcommunications system 100.

There may be different ways to announce the new MBMS bearer. Accordingto some aspects the MBMS bearer identity and complementary serviceannouncement information is announced on demand and in direct responseto the new MBMS bearer being activated. Hence, according to some aspectsstep S106 is performed in direct response to step S104.

Reference is now made to FIG. 6 illustrating a method for MBMS bearerhandling in a group communications system 100 as performed by the clientnode 300 a, 300 b according to an embodiment.

As disclosed above the control node 200 in step S106 announces MBMSbearer identity and complementary service announcement information ofthe new MBMS bearer on an already announced MBMS bearer. It is hereassumed that the client node 300 a, 300 b receives this announcement.Hence, the client node 300 a, 300 b is configured to perform step S204:

S204: The client node 300 a, 300 b obtains a broadcast serviceannouncement of the new MBMS bearer on the already announced MBMS bearerfrom the control node 200 of the group communications system 100. Theservice announcement comprises the MBMS bearer identity and (mandatoryand optional) complementary service announcement information of the newMBMS bearer.

Embodiments relating to further details of MBMS bearer handling in thegroup communications system 100 relating to the client node 300 a, 300 bwill now be disclosed.

Reference is now made to FIG. 7 illustrating methods for MBMS bearerhandling in the group communications system 100 as performed by theclient node 300 a, 300 b according to further embodiments. It is assumedthat step S204 is performed as disclosed above.

There may be different ways for the client node 300 a, 300 b to obtainthe broadcast service announcement. According to some aspects the clientnode 300 a, 300 b monitors the already announced MBMS bearer. Hence,according to an embodiment the client node 300 a, 300 b is configured toperform step S202:

S202: The client node 300 a, 300 b monitors the already announced MBMSbearer upon obtaining the broadcast service announcement. Step S202 isperformed prior to step S204.

The client node 300 a, 300 b is then allowed to be in idle mode whenobtaining the broadcast service announcement in step S204.

There may be different ways for the client node 300 a, 300 b to handlethe complementary information. For example, according to some aspects,the client node 300 a, 300 b combines the complementary information withany previously received service announcement information (if existing).Hence, according to an embodiment the client node 300 a, 300 b isconfigured to perform step S206:

S206: The client node 300 a, 300 b combines the complementary serviceannouncement information with any previously received serviceannouncement information of the new MBMS bearer. The combining generatescomplete service announcement information of the new MBMS bearer. StepS206 is performed after step S204. Here, the complementary serviceannouncement information and the previously received serviceannouncement information can both be regarded as defining partialservice announcement information.

Embodiments which are applicable to the methods for MBMS bearer handlingin the group communications system 100 as performed by both the controlnode 200 and the client node 300 a, 300 b will now be described in turn.

There can be different examples of the already announced MBMS bearer.According to some aspects the already announced MBMS bearer is used bythe control node 200 for transmitting group communication controlmessages in the group communications system 100.

There can be different examples of how to announce the MBMS beareridentity and complementary service announcement information. Accordingto some aspects the MBMS bearer identity and complementary serviceannouncement information is announced using a Real-Time Protocol (RTP),or a Real-time Transport Control Protocol (RTCP).

There can be different examples of complementary service announcementinformation. According to an embodiment the complementary serviceannouncement information comprises group communication streaming mediainitialization parameters of the new MBMS bearer. Here, the streamingmedia initialization parameters could comprise at least one of amulticast Internet Protocol, IP, address, User datagram protocol, UDP,port information, IP source address information of media source, mediaprotocol information, codec information and reference to at least oneother announced MBMS bearer. In this respect the thus listed parameterscan be reused from previous announcements. According to an embodimentthe complementary service announcement information comprises at leastone reference to service announcement information of at least onepreviously announced MBMS bearer.

A particular embodiment for MBMS bearer handling in a groupcommunications system 100 based on at least some of the above disclosedembodiments will now be disclosed in detail with reference to thesignalling diagram of FIG. 9.

A pre-condition for this particular embodiment is a group communicationsystem 100 comprising a group communication application server (GCS AS)as represented by the control node 200) and an MBMS system asrepresented by the BM-SC 135.

S401: One MBMS bearer is activated and announced to the client nodes 300a, 300 b by the control node 200. This MBMS bearer can be used for groupcommunication control messages such as floor control. The client nodes300 a, 300 b in the wireless devices 150 a, 150 b are activelymonitoring this group communication control messages channel. One way toimplement step S401 is to perform step S202.

S402: An MBMS service is (optionally) announced to the client nodes 300a, 300 b by the control node 200 according to any of the definedprocedures for service announcement in 3GPP TS 26.346 v13.2.0. Howeverthe service may be inactive as indicated by scheduling information inthe service announcement information.

S403: A new MBMS bearer is activated by the control node 200 based on aneed for group communication. This new MBMS bearer can be used tobroadcast the group communication data. One way to implement step S403is to perform any of steps S102, S104.

S404: To announce the new MBMS bearer, the control node 200 sends aservice announcement message to the BM-SC 135 in the MBMS system. Thenew MBMS bearer is thus announced on an already announced MBMS bearer.The service announcement message for the new MBMS bearer will bebroadcasted over the radio access network 120 to the wireless devices150 a, 150 b, and thus to the client nodes 300 a, 300 b. This messagemay be carried in a RTCP packet, and can thus be sent on demand, andcontains at least the minimum required parameters for the client nodes300 a, 300 b to be able to start monitoring the new MBMS bearer. Thisincludes the MBMS bearer identity in the form of a Temporary MobileGroup Identity (TMGI), the Session Description Protocol (SDP) for thesession and potentially additional parameters. The SDP includes aMulticast IP address, port, source address, protocol, codec.Additionally this message may include a reference to an alreadyannounced MBMS service. This would allow reuse of other type of featuressuch as scheduling information, error correction procedures, receptionreporting procedures etc. One way to implement step S404 is to performstep S106 and step S204.

FIG. 2a schematically illustrates, in terms of a number of functionalunits, the components of a control node 200 according to an embodiment.Processing circuitry 210 is provided using any combination of one ormore of a suitable central processing unit (CPU), multiprocessor,microcontroller, digital signal processor (DSP), etc., capable ofexecuting software instructions stored in a computer program product 410a (as in FIG. 4), e.g. in the form of a storage medium 230. Theprocessing circuitry 210 may further be provided as at least oneapplication specific integrated circuit (ASIC), or field programmablegate array (FPGA).

Particularly, the processing circuitry 210 is configured to cause thecontrol node 200 to perform a set of operations, or steps, S102-S106,S403, S404, as disclosed above. For example, the storage medium 230 maystore the set of operations, and the processing circuitry 210 may beconfigured to retrieve the set of operations from the storage medium 230to cause the control node 200 to perform the set of operations. The setof operations may be provided as a set of executable instructions. Thusthe processing circuitry 210 is thereby arranged to execute methods asherein disclosed.

The storage medium 230 may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory,optical memory, solid state memory or even remotely mounted memory.

The control node 200 may further comprise a communications interface 220for communications at least with at least one client node 300 a, 300 b.As such the communications interface 220 may comprise one or moretransmitters and receivers, comprising analogue and digital componentsand a suitable number of antennas for wireless communications and portsfor wireline communications.

The processing circuitry 210 controls the general operation of thecontrol node 200 e.g. by sending data and control signals to thecommunications interface 220 and the storage medium 230, by receivingdata and reports from the communications interface 220, and byretrieving data and instructions from the storage medium 230. Othercomponents, as well as the related functionality, of the control node200 are omitted in order not to obscure the concepts presented herein.

FIG. 2b schematically illustrates, in terms of a number of functionalmodules, the components of a control node 200 according to anembodiment. The control node 200 of FIG. 2b comprises a number offunctional modules; an obtain module 210 a configured to perform stepS102, an activate module 210 b configured to perform step S104, and anannounce module 210 c configured to perform step S106. The control node200 of FIG. 2b may further comprise at least one optional functionalmodule. In general terms, each functional module 210 a-210 c may beimplemented in hardware or in software. Preferably, one or more or allfunctional modules 210 a-210 c may be implemented by the processingcircuitry 210, possibly in cooperation with functional units 220 and/or230. The processing circuitry 210 may thus be arranged to from thestorage medium 230 fetch instructions as provided by a functional module210 a-210 c and to execute these instructions, thereby performing stepsS102-S106, S403, S404.

The control node 200 may be provided as a standalone device or as a partof at least one further device. For example, the control node 200 may beprovided in a node of the radio access network 120 or in a node of thecore network 130 or in a node of the service network 140. Alternatively,functionality of the control node 200 may be distributed between atleast two devices, or nodes. These at least two nodes, or devices, mayeither be part of the same network part (such as the radio accessnetwork or the core network or the service network) or may be spreadbetween at least two such network parts. Some examples of where in thecommunications system 100 the control node 200 may be provided areillustrated in FIG. 1.

Functionality of the control node 200 may be implemented at the servicelayer of the protocol stack. In general terms, instructions that arerequired to be performed in real time may be performed in a device, ornode, operatively closer to the radio access network 120 thaninstructions that are not required to be performed in real time. In thisrespect, at least part of the control node 200 may reside in the radioaccess network 120, such as in the radio access network node 110, forcases when embodiments as disclosed herein are performed in real time.

Thus, a first portion of the instructions performed by the control node200 may be executed in a first device, and a second portion of the ofthe instructions performed by the control node 200 may be executed in asecond device; the herein disclosed embodiments are not limited to anyparticular number of devices on which the instructions performed by thecontrol node 200 may be executed. Hence, the methods according to theherein disclosed embodiments are suitable to be performed by a controlnode 200 residing in a cloud computational environment. Therefore,although a single processing circuitry 210 is illustrated in FIG. 2a theprocessing circuitry 210 may be distributed among a plurality ofdevices, or nodes. The same applies to the functional modules 210 a-210c of FIG. 2b and the computer program 420 a of FIG. 4 (see below).

FIG. 3a schematically illustrates, in terms of a number of functionalunits, the components of a client node 300 a, 300 b according to anembodiment. Processing circuitry 310 is provided using any combinationof one or more of a suitable central processing unit (CPU),multiprocessor, microcontroller, digital signal processor (DSP), etc.,capable of executing software instructions stored in a computer programproduct 410 b (as in FIG. 4), e.g. in the form of a storage medium 330.The processing circuitry 310 may further be provided as at least oneapplication specific integrated circuit (ASIC), or field programmablegate array (FPGA).

Particularly, the processing circuitry 310 is configured to cause theclient node 300 a, 300 b to perform a set of operations, or steps,S202-S206, S401, S404, as disclosed above. For example, the storagemedium 330 may store the set of operations, and the processing circuitry310 may be configured to retrieve the set of operations from the storagemedium 330 to cause the client node 300 a, 300 b to perform the set ofoperations. The set of operations may be provided as a set of executableinstructions. Thus the processing circuitry 310 is thereby arranged toexecute methods as herein disclosed.

The storage medium 330 may also comprise persistent storage, which, forexample, can be any single one or combination of magnetic memory,optical memory, solid state memory or even remotely mounted memory.

The client node 300 a, 300 b may further comprise a communicationsinterface 320 for communications at least with a control node 200. Assuch the communications interface 320 may comprise one or moretransmitters and receivers, comprising analogue and digital componentsand a suitable number of antennas for wireless communications and portsfor wireline communications.

The processing circuitry 310 controls the general operation of theclient node 300 a, 300 b e.g. by sending data and control signals to thecommunications interface 320 and the storage medium 330, by receivingdata and reports from the communications interface 320, and byretrieving data and instructions from the storage medium 330. Othercomponents, as well as the related functionality, of the client node 300a, 300 b are omitted in order not to obscure the concepts presentedherein.

FIG. 3b schematically illustrates, in terms of a number of functionalmodules, the components of a client node 300 a, 300 b according to anembodiment. The client node 300 a, 300 b of FIG. 3b comprises an obtainmodule 310 a configured to perform step S204. The client node 300 a, 300b of FIG. 3b may further comprise a number of optional functionalmodules, such as any of a combine module 310 b configured to performstep S206, and a monitor module 310 c configured to perform step S202.In general terms, each functional module 310 a-310 c may be implementedin hardware or in software. Preferably, one or more or all functionalmodules 310 a-310 c may be implemented by the processing circuitry 310,possibly in cooperation with functional units 320 and/or 330. Theprocessing circuitry 310 may thus be arranged to from the storage medium330 fetch instructions as provided by a functional module 310 a-310 cand to execute these instructions, thereby performing steps S202-S206,S401, S404.

The client node 300 a, 300 b may be provided as a standalone device oras a part of at least one further device. For example, the client node300 a, 300 b may be provided in a wireless device 150 a, 150 b. Hence,any processing circuitry, communications interface and storage medium ofthe wireless device 150 a, 150 b may be shared with the processingcircuitry 310, communications interface 320 and storage medium 330 ofthe client node 300 a, 300 b. It is thus not necessary for the clientnode 300 a, 300 b to have its own processing circuitry 310,communications interface 320 and storage medium 330 as long as theprocessing circuitry, communications interface and storage medium of thewireless device 150 a, 150 b is configured to implement thefunctionality of the herein disclosed client node 300 a, 300 b.

FIG. 4 shows one example of a computer program product 410 a, 410 bcomprising computer readable means 430. On this computer readable means430, a computer program 420 a can be stored, which computer program 420a can cause the processing circuitry 210 and thereto operatively coupledentities and devices, such as the communications interface 220 and thestorage medium 230, to execute methods according to embodimentsdescribed herein. The computer program 420 a and/or computer programproduct 410 a may thus provide means for performing any steps of thecontrol node 200 as herein disclosed. On this computer readable means430, a computer program 420 b can be stored, which computer program 420b can cause the processing circuitry 310 and thereto operatively coupledentities and devices, such as the communications interface 320 and thestorage medium 330, to execute methods according to embodimentsdescribed herein. The computer program 420 b and/or computer programproduct 410 b may thus provide means for performing any steps of theclient node 300 a, 300 b as herein disclosed.

In the example of FIG. 4, the computer program product 410 a, 410 b isillustrated as an optical disc, such as a CD (compact disc) or a DVD(digital versatile disc) or a Blu-Ray disc. The computer program product410 a, 410 b could also be embodied as a memory, such as a random accessmemory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM), or an electrically erasable programmableread-only memory (EEPROM) and more particularly as a non-volatilestorage medium of a device in an external memory such as a USB(Universal Serial Bus) memory or a Flash memory, such as a compact Flashmemory. Thus, while the computer program 420 a, 420 b is hereschematically shown as a track on the depicted optical disk, thecomputer program 420 a, 420 b can be stored in any way which is suitablefor the computer program product 410 a, 410 b.

The inventive concept has mainly been described above with reference toa few embodiments. However, as is readily appreciated by a personskilled in the art, other embodiments than the ones disclosed above areequally possible within the scope of the inventive concept, as definedby the appended patent claims.

The invention claimed is:
 1. A method for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system, the method being performed by a control node, the method comprising: obtaining a need for a new MBMS bearer to be activated; activating the new MBMS bearer; and announcing MBMS bearer identity and complementary service announcement information of the new MBMS bearer on an already announced MBMS bearer, thereby announcing the new MBMS bearer.
 2. The method according to claim 1, wherein the new MBMS bearer is activated for supporting media transmission in a group call of the group communications system.
 3. The method according to claim 1, wherein the MBMS bearer identity and complementary service announcement information is announced on demand and in direct response to the new MBMS bearer being activated.
 4. A method for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system, the method being performed by a client node, the method comprising: obtaining a broadcast service announcement of a new MBMS bearer on an already announced MBMS bearer from a control node of the group communications system, wherein the service announcement comprises the MBMS bearer identity and complementary service announcement information of the new MBMS bearer.
 5. The method according to claim 4, further comprising: combining the complementary service announcement information with any previously received service announcement information of the new MBMS bearer so as to generate complete service announcement information of the new MBMS bearer.
 6. The method according to claim 4, further comprising: monitoring the already announced MBMS bearer upon obtaining the broadcast service announcement.
 7. The method according to claim 4, wherein the client node is in idle mode when obtaining the broadcast service announcement.
 8. The method according to claim 4, wherein the already announced MBMS bearer is used by the control node for transmitting group communication control messages in the group communications system.
 9. The method according to claim 4, wherein the MBMS bearer identity and complementary service announcement information is announced using a Real-Time Protocol, RTP, or a Real-time Transport Control Protocol, RTCP.
 10. The method according to claim 4, wherein the complementary service announcement information comprises group communication streaming media initialization parameters of the new MBMS bearer.
 11. The method according to claim 10, wherein the streaming media initialization parameters comprises at least one of a multicast Internet Protocol, IP, address, User datagram protocol, UDP, port information, IP source address information of media source, media protocol information, codec information, and reference to at least one other announced MBMS bearer.
 12. The method according to claim 4, wherein the complementary service announcement information comprises at least one reference to service announcement information of at least one previously announced MBMS bearer.
 13. A control node for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system, the control node comprising processing circuitry, the processing circuitry being configured to cause the control node to: obtain a need for a new MBMS bearer to be activated; activate the new MBMS bearer; and announce MBMS bearer identity and complementary service announcement information of the new MBMS bearer on an already announced MBMS bearer, thereby announcing the new MBMS bearer.
 14. A control node for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system, the control node comprising: processing circuitry; and a computer program product (410 a) storing instructions that, when executed by the processing circuitry, causes the control node to: obtain a need for a new MBMS bearer to be activated; activate the new MBMS bearer; and announce MBMS bearer identity and complementary service announcement information of the new MBMS bearer on an already announced MBMS bearer, thereby announcing the new MBMS bearer.
 15. A client node for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system, the client node comprising processing circuitry, the processing circuitry being configured to cause the client node to: obtain a broadcast service announcement of a new MBMS bearer on an already announced MBMS bearer from a control node of the group communications system, wherein the service announcement comprises the MBMS bearer identity and complementary service announcement information of the new MBMS bearer.
 16. A client node for multimedia broadcast multicast service (MBMS) bearer handling in a group communications system, the client node comprising: processing circuitry; and a computer program product storing instructions that, when executed by the processing circuitry, causes the client node to: obtain a broadcast service announcement of a new MBMS bearer on an already announced MBMS bearer from a control node of the group communications system, wherein the service announcement comprises the MBMS bearer identity and complementary service announcement information of the new MBMS bearer. 